Formulations Having Benzoate Dye Carriers for Meta-Aramid Articles

ABSTRACT

Glycol ether benzoates, glycol benzoates and methyl benzoate facilitate the dyeing of the meta-aramid article, e.g., fibers, at or near neutral pH. The addition of an anionic surfactant, such as sodium lauryl sulfate, enhances the performance of the benzoates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to meta-aramid articles, e.g., fibers, fabricsand the like. In one aspect the invention relates to dyeing meta-aramidarticles while in another aspect the invention relates to facilitatingthe dyeing of meta-aramid articles through the use of benzoate carrier.

2. Description of the Related Art

Meta-aramid articles, e.g., fibers such as NOMEX″ and CONEX™ (bothpolymetaphenylene isophthalic amide, which is formed by the reaction ofmeta-phenylenediamine and isophthaloyl chloride, and produced by DuPontand Teijin respectively), are used in various applications, largely fortheir fire resistant properties. Due to their hydrophobic nature, thesearticles are difficult to dye in typical aqueous dye baths as the dyemolecules cannot easily penetrate the article.

In order to facilitate dye penetration, a carrier (sometimes referred toas a dye assist or solvent) must be used to swell the article andfacilitate dye transport. The first commonly used carrier wasacetophenone but it has fallen from favor due to odor and toxicityissues, and other carriers have been introduced or suggested asalternatives. For example, US 2005/0014435A1 describes the dyeing ofaramid fibers with a dye bath formulated with CYNDAE C-45 (availablefrom Bozzetto, Inc.) as a dye assist. JP 60162883 describes the use of aglycol ether (triethylene glycol monophenyl ether) in a dye bath forpolyamide fibers. WO2006/122887A2 describes the use of another glycolether (1-phenoxy-2-propanol) in the preparation of dye baths.US2002/0144362A1 describes 3,5,5-trimethyl-2-cyclohexen-1-one, alsoknown as isophorone, as a dye carrier for polyamide fibers. This patentalso references alkyl ketones and N-alkyl phthalimides as dye carriers.U.S. Pat. No. 6,132,476 describes the use of benzyl alcohol, N-alkylpyrrolidones, N,N-dialkyl-benzamides, and aryl ether as dye carriers.U.S. Pat. No. 6,840,967 describes the use of ethylene glycol phenylether, and various amides and amines as dye carriers. JP 08134370 A2describes the use of several glycol ethers, namely diethylene glycolmonophenyl ether, ethylene glycol monophenyl ether, ethylene glycolmonobenzyl ether, and diethylene glycol monobenzyl ether as dyecarriers. Butyl benzoate is mentioned as a dye carrier by T. Vigo in“Textiles Processing and Properties—Preparation, Dyeing, Finishing, andPerformance”, Textile Science and technology 11, Elsevier Publishing,1994, p137.

Despite the identification and proposed uses of these many and varieddye carriers, interest remains in identifying new dye carriers for usewith meta-aramid articles, particularly fibers, that are performancecompetitive with acetophenone but without the odor and toxicity issuesassociated with the use of acetophenone.

SUMMARY OF THE INVENTION

Surprisingly, glycol ether benzoates, glycol benzoates and methylbenzoate facilitate the dyeing of a meta-aramid articles at or nearneutral pH. The addition of an anionic surfactant, such as sodium laurylsulfate, enhances the performance of these benzoates.

In one embodiment the invention is an aqueous dye formulationcomprising:

-   -   A. A cationic dye;    -   B. At least one of a glycol ether benzoate, glycol benzoate and        methyl benzoate;    -   C. Water; and    -   D. Optionally, an anionic surfactant.        In one embodiment the dye formulation has a pH of 6-8. In one        embodiment the water is de-ionized.

In one embodiment the invention is a method of dyeing a meta-aramidarticle, the method comprising the step of contacting the meta-aramidarticle with a dye formulation comprising:

-   -   A. A cationic dye;    -   B. At least one of a glycol ether benzoate, glycol benzoate and        methyl benzoate;    -   C. Water; and    -   D. Optionally, an anionic surfactant;        the formulation having a pH of 6-8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Definitions

The numerical ranges in this disclosure are approximate, and thus mayinclude values outside of the range unless otherwise indicated.Numerical ranges include all values from and including the lower and theupper values, in increments of one unit, provided that there is aseparation of at least two units between any lower value and any highervalue. As an example, if a compositional, physical or other property,such as, for example, molecular weight, etc., is from 100 to 1,000, thenall individual values, such as 100, 101, 102, etc., and sub ranges, suchas 100 to 144, 155 to 170, 197 to 200, etc., are expressly enumerated.For ranges containing values which are less than one or containingfractional numbers greater than one (e.g., 1.1, 1.5, etc.), one unit isconsidered to be 0.0001, 0.001, 0.01 or 0.1, as appropriate. For rangescontaining single digit numbers less than ten (e.g., 1 to 5), one unitis typically considered to be 0.1. These are only examples of what isspecifically intended, and all possible combinations of numerical valuesbetween the lowest value and the highest value enumerated, are to beconsidered to be expressly stated in this disclosure. Numerical rangesare provided within this disclosure for, among other things, therelative amounts of the components of the dye bath.

“Comprising”, “including”, “having” and like terms are not intended toexclude the presence of any additional component, step or procedure,whether or not the same is specifically disclosed. In order to avoid anydoubt, all compositions, solutions or baths, processes, etc., claimedthrough use of the term “comprising” may include one or more additionalsteps, pieces of equipment or component parts, and/or materials unlessstated to the contrary. In contrast, the term, “consisting essentiallyof” excludes from the scope of any succeeding recitation any othercomponent, step or procedure, excepting those that are not essential tooperability. The term “consisting of” excludes any component, step orprocedure not specifically delineated or listed. The term “or”, unlessstated otherwise, refers to the listed members individually as well asin any combination.

Dye Carriers

The dye carriers used in the practice of this invention include methylbenzoate, glycol benzoates and glycol ether benzoates.

The glycol benzoates, also known as alkylene glycol dibenzoates,typically have an alkylene group (e.g., —CH₂CH₂—) of 2 to 10 carbonatoms bridging the two benzoic groups (e.g., C₆H₅—(C═O)—O—), moretypically 2 to 6 carbon atoms and even more typically 2 to 4 carbonatoms. Representative glycol benzoates include diethylene glycol mono-and dibenzoates, dipropylene glycol mono- and dibenzoates, triethyleneglycol benzoates and trimethylene glycol dibenzoates.

The glycol ether benzoates used in the practice of this invention are ofthe formula

R¹—O—(CH₂CH(R²O)n-R³

in which R¹ is a C₁₋₁₀ alkyl group, phenyl or benzyl, R² is eitherhydrogen, methyl or ethyl, R³— is O═C—C₆H₅ from benzoic acid, and n=1-3.Representative glycol ether benzoates include1-methoxy-2-propylbenzoate, 2-propoxyethyl benzoate, 2-butoxyethylbenzoate, 2-(2-phenoxyethoxy)ethyl benzoate and2-(2-phenoxy-1-methylethoxy)-1-methylethoxy benzoate.

The benzoates of this invention can be used alone or in combination withone another and/or in combination with one or more other glycols and/orone or more alcohols. Representative blends include a blend of propyleneglycol dibenzoates, or a blend of dipropylene glycol benzoates, or ablend of propylene glycol mono-benzoate, or a blend of a propyleneglycol dibenzoate and a dipropylene glycol benzoate, and the like. Onecommercial blend of interest is BENZOFLEX™ 284 plasticizer which isblend of 1,2-propanediol and dibenzoate available from the EastmanChemical Company and which is typically used with polyvinyl chlorideapplications. Another blend of interest is a blend of methyl benzoateand VELATE™ 368 which is 2-ethyihexyl benzoate and it also availablefrom the Eastman Chemical Company. VELATE™ 368 is typically used inpaint coatings.

In one embodiment the methyl benzoate, glycol benzoate and/or glycolether benzoate dye carrier of this invention is used in combination withone or more anionic surfactants. Any anionic surfactant that willfacilitate the benzoate carrier in delivering the dye to the aramidfiber can be used in the practice of this invention. Representativeanionic surfactants are the linear alkyl sulfonates (e.g., sodium laurylsulfate, sodium decyl sulfate, sodium tetradecyl sulfate), and thevarious DOWFAX™ anionic surfactants available from The Dow ChemicalCompany.

The amount of the glycol ether benzoates, glycol benzoates and/or alkylbenzoates in the dye formulation is typically 3 to 6 percent by weight(wt %), more typically 3.5 to 5 wt %. The amount of surfactant, ifpresent, is typically of 1 to 4 wt %, more typically 1.5 to 3 wt %.

Cationic Dye

A variety of cationic dyes may be used in the practice of thisinvention, and different cationic dyes may be preferred depending on thedye process employed and the article to be dyed.

Representative cationic dyes (sometimes referred to as basic dyes)include ASTRAZON™ Olive Green BL and ASTRAZON™ Orange 3RL (also known,respectively, as Basic Green 6 and Basic Orange 27, and both formerlymanufactured by Verona Dyestuffs) and Basic Yellow 21, Basic Blue 41,and Basic Red 18 (further identified in the color index, third edition,published by the Society of Dyers and Colourists, Dean House, PiccadillyBradford, Yorkshire, England). Also useful as cationic dyes are Red GL,Yellow 5GL, Blue X-3GL-300, and Red FB, sold under the trade nameBASACRYL™ by BASF Corporation. The aqueous formulation might include anycombination of such dyes.

The amount of dye in the dye formulation can vary widely, but typicallythe dye is present in an amount of 0.05 to 5 wt %, more typically in anamount of 0.1 to 1 wt %.

Dye Formulation

The dye formulation used in this invention is an aqueous formulationcomprising (A) a cationic dye, (B) at least one of a glycol etherbenzoate, glycol benzoate and methyl benzoate, (C) water, preferablyde-ionized water, and (D) optionally an anionic surfactant. In oneembodiment, dye formulation used in this invention is an aqueousformulation consisting essentially of (A) a cationic dye, (B) at leastone of a glycol ether benzoate, glycol benzoate and methyl benzoate, (C)water, and (D) optionally an anionic surfactant. The dye formulation canbe either a solution or dispersion under dyeing conditions.

Various additives can be present in the dye formulation, and theseinclude such materials as one or more salts, e.g., sodium nitrate orchloride, and/or emulsifiers, and/or surfactants other than anionicsurfactants, and/or ultraviolet light absorbers, and/or pH adjusters,and/or other glycols, e.g., methoxytriglycol, and/or processing aids,and the like. These additives are well known in the art, and if used,are used in conventional amounts and in conventional ways.

The pH of the formulation is typically of 6 to 8, more typically of 6.3to 6.8. The temperature of the dye formulation, particularly when it isused as an immersion bath, is typically of 120° C. to 170° C., moretypically of 130° C. to 150° C.

The bulk of the dye formulation is, of course, water. If a concentrateof the dye formulation is desired for whatever reason, e.g., shipping,storage, etc., then the amount of water is decreased and the relativeamounts of the other components of the formulation are proportionatelyincreased. To ready for use, water is simply added to the concentrate todilute it to the desire concentration of the other components.

Meta-aramid articles can be dyed using the dye formulation of thisinvention and conventional dying processes. In one embodiment, thearticle, e.g., a fiber, is immersed in a bath of the dye formulationunder conventional dying conditions for a period of time sufficient toallow the dye to penetrate and attach to the fiber, and then is removedfrom the bath and dried. In one embodiment, the fiber is attached to aninternal assembly (designed to hold the fiber) of a cylindrically shapedcontainer, the container filled or partially filled with the dyeformulation bath and sealed, the container then placed on or into anapparatus designed to heat the bath to an appropriate dyeing temperatureand rotate the container over the period of time necessary to effect thedesired level of dyeing (typically measured in hours). At the end of thedyeing cycle, the fiber is retrieved from the container and dried. Inother embodiments the dye formulation can be applied to the article in amanner and under conditions other than typical immersion conditionswhich also allow for the dye to penetrate and attach to the article.

Although the invention is particularly useful for the dying ofmeta-aramid fibers or other such articles, the invention is also usefulfor the dyeing of articles made from other amide polymers including, butnot limited to, para-aramid polymers, e.g., KEVLAR™, and polyamidepolymers, e.g., NYLON™.

SPECIFIC EMBODIMENTS

The equipment used to dye meta-aramid fiber (NOMEX™ from DuPont) allowedthe simultaneous evaluation of 12 individual dye solutions and NOMEX™swatches using only about 20 milliliters (ml) dye solution and swatchesmeasuring 3 centimeters (cm)×3 cm. The apparatus was configured in arotisserie-type assembly. A central axle containing 6 brackets equippedwith spring clamps is secured to brass bushing bearings inside an oven.One of the axle ends protrudes through the bearing outside the ovenwhere it is attached to a variable speed motor. The brackets can eachhold 2 stainless steel ampoules measuring about 6 inches in length and 1inch in thickness. The ampoules are fitted with Swagelok compressionfittings at one end and welded shut at the other, and are rated forgreater than (>) 1000 pounds per square inch gauge (psig) pressure fortests in the 100-160° C. range. When attached to the brackets, theampoules could be rotated end over end to provide suitable mixing andeven dyeing of the swatch. Tests were conducted at 140° C. and 50 rpm.

All tests were conducted in the presence of excess dye. A stock dyeaqueous solution containing 0.1% by weight Basic Blue #3 at pH 6.3(adjusted with 0.1 N NaOH) was prepared and used for all experiments. Ina typical experiment, an ampoule was placed on a lab analytical balanceinside a holder and then 18.81 g of the dye solution was weighed in,followed by 0.80 g 1-methoxy-2-propyl benzoate, and 0.40 g sodium laurylsulfate (SLS). A NOMEX™ swatch weighing 0.19 g was inserted into theampoule which was then secured in a vise and sealed with the Swagelokfitting. The final dye bath contained 4% 1-methoxy-2-propyl benzoate and2% SLS. This procedure was repeated with the next ampoule using thedesired solvent and surfactant. When a surfactant was used, the finalconcentration of surfactant actives was kept at 2% by weight. Allampoules were weighed full and the weights recorded.

The loaded ampoules were placed in the holders and secured with thespring clamps. The oven was turned on and set for 140° C. The motor wasturned on and set for 50 rpm. A timer was set for 1 hour and 27 minutes.When time had elapsed, the oven was cooled to 50° C. and the ampoulesremoved by an operator wearing heat resistant gloves and otherprotective equipment. The ampoules were placed in a bucket with ice tocool them down to room temperature, at which point they were wiped dry,reweighed to ascertain that no contents had been lost, and then opened.

The swatches were removed with tweezers and placed in separate 1-ozglass bottles containing 30 ml de-ionized water and labeledappropriately. The bottles were sealed and placed on a lab shaker for 10minutes, then removed from the shaker, opened, and the rinse waterdiscarded. This procedure was repeated at least two more times until therinse water did not contain any residual blue dye. The swatches werethen removed from the bottles, patted dry with paper towel, placed inlabeled aluminum weighing dishes which were then placed in a 40° C. ovento dry for 40 minutes. When the time had elapsed, the swatches wereremoved from the oven and placed in covered plastic dishes. Care wastaken to keep the dishes away from light as the color of dyed NOMEX™material can be degraded by exposure to light.

A Hunter Lab ULTRASCAN™ Vis colorimeter was used to measure the color ofthe dyed swatches in terms of the L, a, b coordinate system. Thecolorimeter was calibrated with a D65-10 Diffuse 8° white tile providedby the manufacturer. An undyed swatch of NOMEX™ was placed in the centerof a 4.25×4.25 inches black ceramic tile equipped with a mask designedto help position and hold the swatch on the tile. Several readings weretaken and the results averaged. The undyed swatch was replaced with oneof the dyed swatches so that color reading could be taken. Thisprocedure was repeated with all the swatches. Results are summarized inthe Table below.

TABLE Color Data for Dyed Swatches Swatch Color Readings Ex. Solventsand Surfactants Added to Dye Solution L a b 1 Undyed NOMEX Swatch 81.342.41 6.38 2 Blank 43.44 −12.74 −9.49 3 2% SLS 60.8 −26.9 −11.76 4 2%1-phenoxy-2-propanol 36.51 −19.54 −14.79 5 4% 1-phenoxy-2-propanol 30.95−20.64 −15.49 6 4% 1-phenoxy-2-propanol + 2% SLS 37.45 −27.91 −16.27 72% 1-phenoxy-2-propanol + 2% SLS 50.44 −31 −15.92 8 2%1-phenoxy-2-propanol + DOWFAX ™ 2A1 (2% actives) 39.91 −24.19 −17.84 94% 1-methoxy-2-propylbenzoate 42.13 −26.88 −11.97 10 4%1-methoxy-2-propylbenzoate + 2% MTG 39.09 −25.38 −12.2 11 4%1-methoxy-2-propylbenzoate-TERGITOL ™ 15-S-40 (2% actives) 43.45 −24.31−10.95 12 4% 1-methoxy-2-propylbenzoate-2% SLS 29.03 −19.54 −11.4 13 4%2-propoxyethylbenzoate 36.11 22.2 −8.58 14 4% 2-butoxyethyl benzoate35.14 19.2 −6.92 15 4% 2-butoxyethyl benzoate + 2% MTG 33.62 −19.08−4.46 16 4% 2-butoxyethyl benzoate + TERGITOL ™ 15-S-40 (2% actives)41.76 −19.76 −7.4 17 4% 2-butoxyethyl benzoate + 2% SLS 29.73 18.8−11.56 18 4% 2-(2-phenoxyethoxy)ethyl benzoate 33.4 −13.96 −9.12 19 4%2-(2-phenoxy-1-methylethoxy)-1-methylethoxy benzoate 32.39 −22.65 −14.6920 4% 2-(2-phenoxy-1-methylethoxy)-1-methylethoxy benzoate + 2% MTG40.66 −23 −7.5 21 4% 2-(2-phenoxy-1-methylethoxy)-1-methylethoxybenzoate + 43.81 −20.75 −6.05 TERGITOL ™ 15-S-40 (2% actives) 22 4%2-(2-phenoxy-1-methylethoxy)-1-methylethoxy benzoate + 2% SLS 32.68−20.66 −13.44 23 4% Methyl Benzoate 36.97 −15.53 −4.41 24 4% BENZOFLEX ™284 33.26 −13.29 −5.96 25 4% VELATE ™ 368 39.42 −18.25 −4.29 Examples2-25 each contained 0.1% Dye Solution. ™ Trademark of The Dow ChemicalCompany SLS = Sodium lauryl sulfate surfactant (100% actives) MTG =methoxytriglycol TERGITOL ™ 15-S-40 = Linear secondary alcoholethoxylated surfactant (70% in water) DOWFAX ™ 2A1 = Alkyldiphenyl oxidedisulfonate surfactant (45% in water) BENZOFLEX ™ 284 = Mixture ofpropylene glycol dibenzoate, dipropylene glycol dibenzoate and propyleneglycol monobenzoate from Eastman Chemicals VELATE ™ = Mixture ofbenzoate esters from Eastman Chemicals

The Hunter color coordinate system defines color in terms of a grid withcoordinates L, a, and b. The a and b scales range from positive tonegative. The more negative a is, the greener the sample appears, andthe more positive the value, the redder the sample appears. Similarly,the more negative b is, the bluer the color shade, and the more positivethe value, the yellower the color shade. The L scale ranges from 0(black) to 100 (white). The lower the L value, the darker the colorshade and the better the depth of color. Thus, lower L values areindicative of improved dye penetration into the fibers.

As can be seen from the data in Table, the undyed swatch (Example 1) hada very high L value (81.34) and a positive b value indicative of poordyeing (as expected in an undyed sample). The use of the dye solutionwithout solvents or surfactants (Example 2) resulted in some dyeing withan L value of 43.4. Addition of 2% sodium lauryl sulfate (SLS) to thedye solution (Example 3) did not improve the dye penetration andactually made it worse as indicated by an L value of 60.8. Addition of1-phenoxy-2-propanol, a well know dye assist, to the dye solution at the2% (Example 4) or 4% level (Example 5) improved the dyeing performanceas indicated by L values of 36.5 and 30.95 respectively. Combining thissolvent with SLS or DOWFAX^(tm) 2A1 actually resulted in poorerperformance (Example 6-8).

As can be seen, dye bath solutions containing 4% glycol ether benzoates(Examples 9, 13, 14, 18, 19) provided good dyeing performance asevidenced by L values as low as 32.39 which are comparable to thoseobtained with 1-phenoxy-2-propanol. Surprisingly, combining these glycolether benzoates with SLS (Examples 12, 17, and 22) improved the depth ofcolor beyond that obtained with the 1-phenoxy-2-propanol control asindicated by L values lower than 30.0. The addition of DOWFAX™ 2A1 orMTG had a small effect while the addition of the nonionic surfactantTERGITOL™ 15-S-40 was actually detrimental. BENZOFLEX™ 284 (a blend ofglycol dibenzoates and mono-benzoates from Eastman Chemical Company),VELATE™ 368 (a benzoate ester from Eastman Chemical Company), and methylbenzoate are also shown as good dye carriers.

1. An aqueous dye formulation comprising: A. A cationic dye; B. At leastone of a glycol ether benzoate and glycol benzoate; C. Water; and D.Optionally, an anionic surfactant.
 2. The dye formulation of claim 1having a pH of 6-8.
 3. The dye formulation of claim 1 in which theglycol ether benzoate is of the formulaR¹—O—(CH₂CH(R²O)_(n)—R³ in which R¹ is a C₁₋₁₀ alkyl group, phenyl orbenzyl, R² is either hydrogen, methyl or ethyl, R³— is C═C—C₆H₅ frombenzoic acid, and n=1-3.
 4. The dye formulation of claim 3 in which thedye is present in an amount of 0.05 to 5 wt %, the at least one of aglycol ether benzoate and glycol benzoate is present in an amount of 3to 6 wt %, and the water is de-ionized.
 5. The dye formulation of claim4 in which the glycol ether benzoate is at least one of1-methoxy-2-propylbenzoate, 2-propoxyethyl benzoate, 2-butoxyethylbenzoate, 2-(2-phenoxyethoxy)ethyl benzoate and2-(2-phnoxy-1-methylethoxy)-1-methylethoxy benzoate; and the glycolbenzoate is at least one of a diethylene glycol mono- and dibenzoates,dipropylene glycol mono- and dibenzoates, triethylene glycol benzoatesand trimethylene glycol dibenzoate.
 6. The dye formulation of claim 5 inwhich the anionic surfactant is present in an amount of 1-4 wt %.
 7. Thedye formulation of claim 6 in which the anionic surfactant is a linearalkyl sulfonate.
 8. A method of dyeing a meta-aramid article, the methodcomprising the step of contacting the meta-aramid article with a dyeformulation comprising: A. A cationic dye; B. At least one of a glycolether benzoate and glycol benzoate; C. Water; and D. Optionally, ananionic surfactant; the dye formulation having a pH of 6-8.
 9. Themethod of claim 8 in which the article is immersed in a bath of the dyeformulation.
 10. . A meta-aramid article dyed by the method of claim 8.11. . The article of claim 10 in the form of a fiber.